Lightweight wedge design for high speed generators

ABSTRACT

A wedge-shaped member to restrain coil windings of a generator rotor from moving under centrifugal force. The wedge-shaped, substantially hollow member including a first plate, a second plate positioned opposite the first plate and positioned at an angle relative to the first plate, and one or more reinforcing members coupled between the first plate and the second plate. The wedge-shaped member is configured to fit between the core poles of a generator. A plurality of holes in the first and/or second plates permit a bonding material to adhere to adjacent coil windings and spread through the holes.

FIELD OF THE INVENTION

Various embodiments of the invention pertain to electric generators andmotors. More particularly, one embodiment of the invention pertains to awedge design for high speed electric generators.

DESCRIPTION OF RELATED ART

Wound-type induction machines have long been used as electric generatorsand motors. In a typical generator design, a direct current (DC) woundrotor includes a magnetic core with multiple poles, each wrapped with acoil. Such rotor spins at high revolutions per minute (RPM) and subjectsits components to high centrifugal loads. To prevent the coils frombeing spun off the core, wedges are employed in the inter-polar area. Athigh RPM (>12,000 RPM) the stress in the pole tips of the rotor core maybe high enough to prevent them from being used to support the wedge. Theloads that are experienced by the wedge in these conditions are thoseimposed by the coil and also those resulting from the centrifugal loaddue to the bulk mass and also the center of mass of the wedge itselfrelative to the axis of rotation of the rotor. These two design factorsare controlled by the shape of the design and the density of thematerial. In a conventional wedge design these conditions result in aconflicting design where the wedge gains weight in order to have enoughstrength to resist the forces it is subjected to. This additional weightthen increases the forces resulting in a vicious circle with thickerwebs being used to provide stiffness merely to provide the stiffness tosupport the wedge itself.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a generator wedge according to one embodiment of theinvention.

FIG. 2 illustrates a rear view of the generator wedge of FIG. 1according to one embodiment of the invention.

FIG. 3 illustrates a cross-sectional view of the generator wedge of FIG.1 according to one embodiment of the invention.

FIGS. 4, 5, and 6 illustrate how a generator wedge may be positionedwithin a generator according to one embodiment of the invention.

SUMMARY OF THE INVENTION

One embodiment of the invention provides a wedge-shaped member torestrain coil windings of a generator rotor from moving undercentrifugal force. The wedge-shaped member includes a first plate, asecond plate opposite the first plate but at an angle to the firstplate, and one or more reinforcing members coupled between the firstplate and the second plate and substantially perpendicular to the firstplate and second plate. The wedge-shaped member is configured to fitbetween the core poles of a generator.

One embodiment of the invention may be implemented in a generator havinga substantially cylindrical rotor frame, a plurality of core polescoupled around the rotor frame, the plurality of core poles extendingradially from the rotor and having core pole tips that are wider thanthe core poles. A coil is wound around a first core pole and awedge-shaped member positioned between the first core pole and a secondcore pole to support the coil on the first core pole as the rotor frameis rotated. The wedge-shaped member includes a first plate having aplurality of through-holes, the first plate abutting the first corepole, a second plate abutting the second core pole. A third plate has afirst longitudinal edge coupled along a first longitudinal edge of thefirst plate and a second longitudinal edge of the third plate coupled toa first longitudinal edge of the second plate. One or more reinforcingcross members are coupled between a second longitudinal edge of thefirst plate and a second longitudinal edge of the second plate to thethird plate. The coil wound around the first core pole is restrained bya bonding material impregnated between the coil and the one or morepassages through the first plate.

According to one embodiment of the invention, the wedge-shaped memberhas a substantially trapezoidal cross-sectional area. The third platemay have a curvature that conforms to the cylindrical rotor frame.

In one embodiment of the invention, the second longitudinal edge of thefirst plate is retained by the core pole tip of the first core pole andthe second longitudinal edge of the second plate is retained by the corepole tip of the second core pole.

DETAILED DESCRIPTION

Devices and apparatus that implement the embodiments of the variousfeatures of the invention will now be described with reference to thedrawings. The drawings and the associated descriptions are provided toillustrate embodiments of the invention and not to limit the scope ofthe invention. Reference in the specification to “one embodiment” or “anembodiment” is intended to indicate that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least an embodiment of the invention. The appearancesof the phrase “in one embodiment” or “an embodiment” in various placesin the specification are not necessarily all referring to the sameembodiment. Throughout the drawings, reference numbers are re-used toindicate correspondence between referenced elements. In addition, thefirst digit of each reference number indicates the figure in which theelement first appears.

In the following description, certain terminology is used to describecertain features of one or more embodiments of the invention. The term“windings” includes wound-type coils and similar devices. The term“generator” includes motors, electrical generators, induction machines,etc.

One embodiment of the invention provides a wedge to fit between poles toprevent coils from being spun off the core.

FIG. 1 illustrates a generator wedge according to one embodiment of theinvention. The wedge 100 has a trapezoidal shape to fit between therotor coils of a generator. The wedge 100 is substantially hollow orincludes a plurality of cavities 108 to keep the center of mass of thegenerator as close to the axis of rotation as possible. Such hollowwedge configuration avoids increasing the loads on the wedge 100 in ahigh speed generator. By having a hollow body or a plurality of cavities108, the wedge's center of mass is moved closer to the generator's axisof rotation thereby reducing the centrifugal load generated by theweight of the wedge 100 itself. As a result, the shape of the wedge 100may be optimized for strength and weight.

A plurality of webs or support cross members 102 provide support to thecoils of a generator at multiple points along the span of the core. Inbetween the webs or cross members 102, thin side walls 104 and 106 areused to hold the webs 102 in position between the generator coils.

The number of webs 102 and/or spacing between the webs 102 may bedictated by the coil loads that the wedge 100 is expected to resist.This configuration eliminates most of the weight found in existing wedgedesigns.

According to one embodiment of the invention, a pattern of holes 110 aredefined by the side walls 104 and 106. These holes 110 further reduceweight and also help resist movement of the wedge 100 by keying animpregnation material between the wedge 100 and the coil insulation. Theimpregnation material binds to the coils as well as flows through theholes 110 to create a strong bond between the coils and side walls 104and 106. Moreover, a radius member 112 at each end of the wedge 100 mayserve to couple the wedge 100 to a generator rotor.

Additionally, the substantially hollow wedge 100 may also improvecooling of the rotor coils due to the shorter heat conduction path andgreater wetted area for the cooling medium to impinge upon. That is, incontrast to a conventional solid wedge, the wedge 100 having a hollowarea or a plurality of cavities 108 reduces the amount of materialthrough which heat from the coils must travel before it is dissipated.Also, the additional surface area formed by the surfaces inside thecavities 108 increases the area through which heat from the rotor coilsmay be dissipated.

FIG. 2 illustrates a rear view of the generator wedge of FIG. 1according to one embodiment of the invention. The short side 202 of thetrapezoid-shaped wedge 100 is typically inserted in between rotor coilsso that it is the closest to the generator's axis of rotation. Asillustrated in FIG. 2, the holes 110 extend from one side of the sidewalls 104 and 106 to the other side.

FIG. 3 illustrates a cross-sectional view of the generator wedge of FIG.1 according to one embodiment of the invention. The angle between theside walls 104 and 106 and short side 202 of the wedge 100 may varydepending on the physical dimensions of the rotor coils for thegenerator in which the wedge 100 is to be used. The web or support crossmembers 102 may extend from the short side 202 to the long side 204 ofthe wedge 100. In other implementations, the web 102 may partiallyextent between the short side 202 to the long side 204 of the wedge 100.In other embodiments of the invention, the web 102 may also include aone or more openings or holes for further ventilation or to reduce theoverall weight of wedge 100.

FIGS. 4, 5, and 6 illustrate how a generator wedge 100 may be positionedwithin a generator 400 according to one embodiment of the invention. Thewedge 100 is placed between to rotor core poles 402 and 404 as shown.Coils 502 and 504 are wound around the first and second cores poles 402and 404 respectively. The generator 400 rotates about an axis 406.Typically, a wedge 100 is placed between every core pole to providesupport to the coils wound thereon.

In one implementation of the invention, the generator 400 includes corepoles 402 and 404 having pole tips 506 and 508 that may serve to providesupport to the wedge 100 when the generator 400 rotates about its axis406. The wedge 100 may be designed so that it fits snugly between thecore poles 402 and 404 and the core poles tips 506 and 508, which retainthe wedge 100 as the generator spins. In this manner, high-speedgenerators can use the core pole tips 506 and 508 to provide support tothe wedge 100 along its entire length. As a result of the supportprovided by the pole tips 506 and 508, the wedge 100 is not required tobe as stiff, thus permitting the thick webs seen at the top of manyconventional wedges to be eliminated, further reducing the weight of thewedge 100.

In one embodiment of the invention, a radius member 112 may be machinedat each end of the wedge 100. When the wedge 100 is inserted into theinter-pole cavities of a generator rotor 400, the wedge 100 may besecured to the generator rotor 400 by bands 602 around the perimeter thegenerator rotor 400 that secure the radius member 112 of the wedges.

Various embodiments of the wedge 100 may be used directly in place ofany conventional wedge once it has been determined that the core poletips have sufficient strength margin to support these wedges 100. Invarious embodiments of the invention, manufacture of this type of wedge100 can be achieved by machining, casting/molding or fabrication.Different materials can be used to make the wedge 100, including metals(e.g., aluminum, steel, and/or titanium) and/or reinforced epoxyplastics such as PEEK. One embodiment of the invention uses the lightestweight material combined with a suitable manufacturing process toachieve the strength required for the desired application. In manycases, this would take the form of a molded reinforced epoxy plastic.

In various embodiments of the invention, the wedges 100 and coils 502and 504 may have a bonding or securing material between them. Forinstance, an epoxy may be impregnated between side wall 106 of wedge 100and the abutting surface of coil 502 so that the epoxy also passesthrough holes 110. This prevents the coils 502 and 504 from loosening orbeing deformed by the centrifugal force of a high speed generator.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat this invention not be limited to the specific constructions andarrangements shown and described, since various other changes,combinations, omissions, modifications and substitutions, in addition tothose set forth in the above paragraphs, are possible. Those skilled inthe art will appreciate that various adaptations and modifications ofthe just described preferred embodiment can be configured withoutdeparting from the scope and spirit of the invention. Therefore, it isto be understood that, within the scope of the appended claims, theinvention may be practiced other than as specifically described herein.

1. A wedge-shaped member, configured to fit between core poles of agenerator to restrain coil windings from moving under centrifugal force,comprising: a first plate having at least one through-hole; a secondplate positioned opposite the first plate and positioned at an anglerelative to the first plate; and one or more reinforcing members coupledbetween the first plate and the second plate and substantiallyperpendicular to the first plate and second plate.
 2. The wedge-shapedmember of claim 1 further comprising a third plate having a firstlongitudinal edge and a second longitudinal edge, the first longitudinaledge of the third plate coupled along a first longitudinal edge of thefirst plate and the second longitudinal edge of the third plate coupledto a first longitudinal edge of the second plate.
 3. The wedge-shapedmember of claim 2 wherein the first and second plates are substantiallyrectangular and the one or more reinforcing members are plates extendingfrom a second longitudinal edge of the first plate and a secondlongitudinal edge of the second plate to the third plate.
 4. Thewedge-shaped member of claim 1 wherein the at least one through-holepermits a quantity of bonding material to pass to restrain the coilwindings.
 5. The wedge-shaped member of claim 1 wherein the second platealso includes at least one through-hole.
 6. A generator comprising: arotor frame; a first and second of core poles coupled to the rotorframe; a coil wound around the first core pole; and a wedge-shapedmember positioned between the first core pole and the second core poleto support the coil on the first core pole as the rotor frame isrotated, the wedge-shaped member including a first plate abutting thefirst core pole, a second plate abutting the second core poles, and oneor more cross members coupled between the first plate and the secondplate.
 7. The generator of claim 6 wherein the rotor frame issubstantially cylindrical and has a first axis of rotation, the firstand second of core poles extending radially from the rotor frame alongthe length of the rotor frame.
 8. The generator of claim 6 furthercomprising a second coil wound around the second core pole.
 9. Thegenerator of claim 6 wherein the first core pole has a core pole tipthat is wider than the core pole, the core pole tip configured to securethe wedge-shaped member in place.
 10. The generator of claim 6 whereinthe wedge-shaped member has a substantially trapezoidal cross-sectionalarea.
 11. The generator of claim 10 further comprising a third platecoupled between a first edge of the first plate and a first edge of thesecond plate, the third plate positioned along the short side of thetrapezoidal wedge-shaped member to abut the rotor frame.
 12. Thegenerator of claim 11 wherein the third plate has a curvature thatconforms to the rotor frame.
 13. The generator of claim 6 wherein thefirst plate, the second plate and the one or more cross members defineone or more cavities within the wedge-shaped member.
 14. The generatorof claim 6 wherein the first plate includes one or more passagesextending from a first surface to a second surface.
 15. The generator ofclaim 14 wherein the coil wound around the first core pole is restrainedby a bonding material impregnated between the coil and the one or morepassages through the first plate.
 16. The generator of claim 6 furthercomprising one or more bands configured to couple around thecircumference of the rotor frame and secure the wedge-shaped member tothe rotor frame.
 17. A generator comprising: a substantially cylindricalrotor frame; a plurality of core poles coupled around the rotor frame,the plurality of core poles extending radially from the rotor and havingcore pole tips that are wider than the core poles; a coil wound around afirst core pole of the plurality of core poles; and a wedge-shapedmember positioned between the first core pole and a second core pole tosupport the coil on the first core pole as the rotor frame is rotated,the wedge-shaped member including a first plate having a plurality ofthrough-holes, the first plate abutting the first core pole, a secondplate abutting the second core pole, a third plate having a firstlongitudinal edge and a second longitudinal edge, the first longitudinaledge of the third plate coupled along a first longitudinal edge of thefirst plate and the second longitudinal edge of the third plate coupledto a first longitudinal edge of the second plate one or more reinforcingcross members coupled between a second longitudinal edge of the firstplate and a second longitudinal edge of the second plate to the thirdplate.
 18. The generator of claim 17 wherein the second longitudinaledge of the first plate is retained by the core pole tip of the firstcore pole and the second longitudinal edge of the second plate isretained by the core pole tip of the second core pole.
 19. The generatorof claim 17 wherein the third plate is curved to conform to thecylindrical rotor frame.
 20. The generator of claim 17 wherein the coilwound around the first core pole is restrained by a bonding materialimpregnated between the coil and the one or more passages through thefirst plate.